Various materials have been used as energy absorbing materials throughout history. Energy absorbing materials can be traced back to armor used in warfare and in other various applications. A typical and early energy absorbing material for armor was leather, although other materials, such as metals and combinations of metals, fabrics, leathers, and other like materials have been used in armor applications to absorb energy from a strike or blow.
Leather had been used as a standard energy absorbing material into the twentieth century, and was used to make body armor and helmets, including football helmets. Indeed, leather had been used as standard energy absorbing materials in the National Football League when players started adopting helmets for use in games, although the mandating of the use of helmets did not occur until many years after the start of the NFL. Better energy absorbing materials have been developed over time for many different applications requiring energy absorption, including combinations of leather and pads, plastics, and air and fluid-filled bladders. Modern era plastics and foams have been utilized for many years as energy absorbing materials, including, for example, Kevlar®, thermoplastic or thermoset foams, and other thermoplastic and thermoset materials have been developed.
It is often difficult to utilize an effective energy absorbing material that is relatively lower profile. In other words, effective energy absorbing materials typically are bulky and difficult to incorporate into armor, helmets, and other applications, especially in applications where space is constrained. Generally, the rule is that the bulkier the material, the better the energy absorbing qualities. However, the bulkier the material, the more difficult it may be for a user to maneuver effectively. For example, in armor and/or helmets, such as for military personnel or football players, bulkier pads and helmets decrease the ability of users to move effectively, slowing them down and making them less able to replicate complex moves during battle or game-day conditions. A need, therefore, exists for energy absorbing apparatuses that reduce the overall size of the articles they are incorporated in, such as armor or helmets. Specifically, a need exists for energy absorbing apparatuses that may easily be incorporated into the applications without compromising energy absorbing properties.
Foams and other like materials are often used in energy absorbing applications. Foam is typically made by introducing air or another gas into a thermoplastic or thermoset material, forming a material with tiny gas-filled open or closed cells disposed throughout the material. In some cases, foams can retain a memory such that the foams absorb an amount of energy and then return to their original shapes, releasing stored potential energy as kinetic energy in the process. In other cases, foams merely deflect upon receiving energy, such as a blow or impact, without returning to their original shape or position. Typically, a foam that destructively absorbs energy may be a better energy absorbing material than a foam that returns to its original shape. However, a foam that destructively absorbs energy can only be used once. Moreover, foams typically dissipate energy by compressing, which merely attempts to “slow down” the impact in the vertical direction. A need exists for energy absorbing apparatuses that dissipate energy from the vertical direction by translating the energy to the horizontal direction, and therefore to prevent energy from transferring vertically to a user or an object.
It can be advantageous for a foam to return to its normal shape, size and/or position after absorbing energy from an impact so that the foam can effective “reset”, allowing the foam to receive additional energy. However, it is often difficult for a foam to quickly and efficiently return to its original shape. Moreover, in many cases, foams do not return completely to their original shapes, sizes and/or positions, making them less effective to absorb the next blow or impact. A need, therefore, exists for energy absorbing apparatuses that quickly and efficiently return to their normal position after receiving a blow or impact. Specifically, a need exists for energy absorbing apparatuses that provide a large amount of energy absorption, but can be used more than once. More specifically, a need exists for energy absorbing apparatuses that can effectively reset themselves after a blow or an impact to be ready to receive another blow or impact.
Foams also suffer because they may retain heat, which may be undesirable in certain applications, such as in military applications or for athletes. A need, therefore, exists for an energy absorbing apparatuses that do not retain heat. Oftentimes, certain materials, such as foams and the like, may be dissolvable in water, which may limit their applications. A need exists for an energy absorbing apparatuses that are waterproof.